There has been known a submersible aerator in which, by means of a negative-pressure self-suction action of an impeller rotating within a liquid storage tank, the impeller draws air from the atmosphere via an air conduit, draws wastewater that flows into the tank (hereinafter referred to as “liquid to be processed”), mixes it with the suctioned air, and jets the air-liquid mixture within the tank to thereby cause an aeration action. The impeller has a special structure, i.e., it includes air suction passages for drawing air and liquid suction passages for drawing the liquid to be processed. With the expectation that large solid materials that have entered within wastewater will be removed by means of a screen facility provided upstream of the liquid storage tank, the conventional submersible aerator is not provided with a strainer or similar member having a function of removing such foreign materials (hereinafter referred to as “foreign objects”) which cannot be removed by the screen facility. In order to address problems of a submersible aerator caused by suction of foreign objects, a detaching mechanism (see, for example, Patent Document 1) or a cutting mechanism for cutting foreign objects (see, for example, Patent Document 2) is provided.
Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. S54-063542 (FIGS. 1 to 5)
Patent Document 2: Japanese Utility Model Publication (kokoku) No. S61-004720 (FIGS. 1 to 4)